Question: The sum of $4$ consecutive odd numbers is $80$. What is the third number in this sequence?
Explanation: Call the first number in the sequence $x$ The next odd number in the sequence is $x + 2$ The sum of the $4$ consecutive odd numbers is: $x+ (x + 2)+ (x + 4)+ (x + 6) = 80$ $4x + 12= 80$ $4x = 68$ $x = 17$ Since $x$ is the first number, $x + 4$ is the third odd number. Thus, the third number in the sequence is $21$.